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WASHINGTON — A former White House official accused of improperly editing reports on global warming defended his editing changes Monday, saying they reflected views in a 2001 report by the National Academy of Sciences.

House Democrats said the 181 changes made in three climate reports reflected a consistent attempt to emphasize the uncertainties surrounding the science of climate change and undercut the broad conclusions that man-made emissions are warming the earth.

Philip Cooney, former chief of staff at the White House Council on Environmental Quality, acknowledged at a House hearing that some of the changes he made were "to align these communications with the administration's stated policy" on climate change.

The extent of Cooney's editing of government climate reports first surfaced in 2005. Shortly thereafter, Cooney, a former oil industry lobbyist, left the White House to work at Exxon Mobil Corp.

"My concern is that there was a concerted White House effort to inject uncertainty into the climate debate," said Rep. Henry Waxman, D-Calif., chairman of the House Government Reform Committee.

Cooney's appearance before Waxman's committee Monday was the first time he has spoken publicly, or was extensively questioned, about the issue.

Cooney said that many of the changes he made to the reports — such as uncertainty about the regional impact of climate change and limits on climate modeling — reflected findings of a 2001 National Academy of Sciences report on climate.

Hansen also testifiesWaxman's committee also heard from James Hansen, director of NASA's Goddard Institute for Space Studies and one of the country's leading climate scientists, who said the White House repeatedly tried to control what government scientists say to the public and media about climate change.

"Interference with communications of science to the public has been greater during the current administration than at any time in my career," said Hansen, who was one of the first to raise concerns about climate change in the 1980s.

Hansen's battles with NASA and White House public affairs officials are not new and resulted in an easing of NASA's policies toward scientists talking to the media about their work.

But that was not always the case.

Hansen said that in 2005 he was told by a 24-year-old NASA public affairs official he could not take part in an interview with National Public Radio on orders from senior NASA public affairs officials. Instead, three other NASA officials were offered for the interview.

The young press officer, George Deutsch, now 26, sat next to Hansen at the witness table Monday and told the committee he had simply been "relaying" the views of higher-ups at NASA that Hansen was not to participate in the interview.

Rep. Darrell Issa, R-Calif., suggested that Hansen was not being muzzled at all and that there is nothing wrong with government scientists being subject to some limits in what they say.

"You're speaking on federal paid time. Your employer happens to be the American taxpayer," Issa lectured Hansen. He said a Google search had shown Hansen cited on more than 1,400 occasions over a year in interviews and appearances.

Hansen said he accepted only "a small fraction" of the requests for interviews and appearances and that, as a matter of free speech, government scientists should not be restrained in their remarks or have public affairs officers listening in on interviews.

"It doesn't ring true," said Hansen. "It's not the American way. And it's not constitutional."

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